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That`s pretty poor *for highway mileage*....most of us get high twenties to low thirties depending on our personal driving habits. How do you calculate your mileage ?
You should pull the plugs to see what they look like....if they`re a nice light greyish-tan color, that would indicate a healthy burn condition....darker, oily plugs are indicative of other things, like maybe a failing CVV.

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Thanks for the reply. I could be totally wrong, but I'm going off of what my dashboard tells me. It says 19.4 mpg which I've assumed is my mileage. What do you mean by the plugs?

Have you recently reset the mpg indicator (press the mode button to display the mpg, then press and hold it until it resets)? If not, that 19.4 is a long term average, not just what you're getting on the highway, and is a reasonable for a suburban or urban environment. Get on the highway on a relatively flat and straight stretch, and then reset the OBC and see what you car is really capable on the highway.

Thanks for the reply. I could be totally wrong, but I'm going off of what my dashboard tells me. It says 19.4 mpg which I've assumed is my mileage. What do you mean by the plugs?

spark plugs

Quote:

Originally Posted by cwsqbm

Have you recently reset the mpg indicator (press the mode button to display the mpg, then press and hold it until it resets)? If not, that 19.4 is a long term average, not just what you're getting on the highway, and is a reasonable for a suburban or urban environment. Get on the highway on a relatively flat and straight stretch, and then reset the OBC and see what you car is really capable on the highway.

+1, also, you need to check your average MPH..duh, c'mon man!
There is a direct correlation between your avg MPH and your MPG. I drive 80 miles a day round trip to work and get 28.00MPG, on my 330ci, but my avg speed is 45.6
Look at your average MPH and reset it the same time you reset your MPG as MPG is definitely impacted by city vs rural driving- I am obviously more rural with an overall average of 45.6.

Thanks for the replies! I've heard that there are some ways to increase your gas mileage by inflating tires and such, can anyone give me some tips on that?

Do make sure your tires are properly inflated. Do not overinflate them.

There are all sorts of crazy ways to increase your mpg, but none better than making sure your car is running as it was designed to.

A loss of mpg is typically resultant of a drop in power. Thus necessitating more work be done by the engine to move the vehicle a given distance. Typically, this is due to one of three things performing below specifications: your volumetric efficiency, combustion efficiency, and mechanical efficiency. Toss in mean effective pressure in case you have a compression issue.

Volumetric efficiency is related to how well your cylinders draw in fuel and air during the induction stroke. Verify that your air filter is not restricting incoming air and that your fuel filter or injectors are not restricting your fuel. Running rich or lean will hurt mpg.

Combustion efficiency is related to how completely the air/fuel mixture burns upon ignition. Lack of total combustion could signal issues with the spark plugs but could also be a lack of sufficient vaporization of the fuel within the air component of the mixture. This again points to injectors.

Finally, mechanical efficiency is, of course, the percentage of work produced by the engine which is actually used to move your car forward and overcome counteracting forces. This is where tire pressure comes into play. Lower tire pressure adds rolling resistance and thus leaches some of your power. Compared to the other items on this list, it's a relatively low culprit. Good lubrication is essential to maintaining peak mechanical efficiency.

Finally, mean effective pressure - if you don't have good compression because of a blown head gasket or something, you won't be able to harness the explosive pressure exerted on the piston and effectively transfer the combustion into work. It's like blowing up a balloon with a hole in it.

Correction: a loss in power will not necessitate more work be done by the engine to move the car a given distance. What I should have said was that more chemical energy will be required to produce the same amount of mechanical work.

Unless the problem is with mechanical efficiency - then my original statement stands.

Try this. It will not take up too much time to accomplish. When you are on a clear freeway, drive at a constant speed, say 65mph. Scroll the OBC to mpg, reset it, then drive for a minute or so. You should get mpg reading of around 30mpg or a little greater. If not, then you have a problem.

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Manually calculating your MPG is the best way to get per tank numbers and average overtime... I use Fuelly every time I fill up and it keeps track for me... it is fairly close to my OBC, off by about 0.2mpg between the Fuelly and OBC.

Manually calculating your MPG is the best way to get per tank numbers and average overtime... I use Fuelly every time I fill up and it keeps track for me... it is fairly close to my OBC, off by about 0.2mpg between the Fuelly and OBC.

That's what i do. Calculate manually.
Always write down mileage when i fill up and how much fuel exactly went in. I have note book for the purpose, also writing down mileage of each service procedure, that way it's easy to check afterwards what was done when.

It may depend on where you live and what time of year it is. I do not do a ton of highway driving, mostly back roads, but normally I get around 23mpg. At least until winter hits. I live north of Boston, and when January and February roll around, I have seen my millage drop to 18. I attribute it to winter gas, but more to the fact that I have to haul around a transfer case, and all the outer running gear for an xi.
We had a warm spell here, and during that time my millage improved.

So if you are in a cold climate, see how the car does in the spring. In the mean time, definitely follow the advice from the other folks.

Frankly 19.4 is extremely low. Do you stick to a steady speed? I just did a 250 mile trip this weekend doing anywhere from 75 to 85 all highway and had 29 to 32 mpg. I did inflate my tires before leaving but I doubt that had much to do with it.

In June I made a trip to myrtle beach sc to our second home which is over 9 hours away an averaged over 34 mpg driving a steady 80-85mph on the highway. I am always careful I leave my foot steady. If your constantly dropping your foot to gain speed your mpg go way down.

Things I have done, replace spark plugs, filters, and fuel filter. I did gain mpg after replacing my fuel filter. And I always leave for a trip with a full tank if gas and recent my miles through my nav screen.

Do make sure your tires are properly inflated. Do not overinflate them.

There are all sorts of crazy ways to increase your mpg, but none better than making sure your car is running as it was designed to.

A loss of mpg is typically resultant of a drop in power. Thus necessitating more work be done by the engine to move the vehicle a given distance. Typically, this is due to one of three things performing below specifications: your volumetric efficiency, combustion efficiency, and mechanical efficiency. Toss in mean effective pressure in case you have a compression issue.

Volumetric efficiency is related to how well your cylinders draw in fuel and air during the induction stroke. Verify that your air filter is not restricting incoming air and that your fuel filter or injectors are not restricting your fuel. Running rich or lean will hurt mpg.

Combustion efficiency is related to how completely the air/fuel mixture burns upon ignition. Lack of total combustion could signal issues with the spark plugs but could also be a lack of sufficient vaporization of the fuel within the air component of the mixture. This again points to injectors.

Finally, mechanical efficiency is, of course, the percentage of work produced by the engine which is actually used to move your car forward and overcome counteracting forces. This is where tire pressure comes into play. Lower tire pressure adds rolling resistance and thus leaches some of your power. Compared to the other items on this list, it's a relatively low culprit. Good lubrication is essential to maintaining peak mechanical efficiency.

Finally, mean effective pressure - if you don't have good compression because of a blown head gasket or something, you won't be able to harness the explosive pressure exerted on the piston and effectively transfer the combustion into work. It's like blowing up a balloon with a hole in it.

To summarize, check your plugs.

Beautifully broken down. +1. Any specific brand you guys would recommend through personal experience, or is there a pretty clear choice for the best spark plugs? I'm looking to get some today after work.